Heat dissipating means for electron microscopes



April 1, 1947. P. (3. SMITH' 2,418,321

HEAT DISSIPATING MEANS FOR ELECTRON MICROSCOPES Filed Dec. 50, 1944 s INVENTOR. PERRY C..SM|T'H ATTORNEY.

Patented Apr. 1, 1947 HEAT DISSIPATING MEANS FOR ELECTRON MICROSCOPES Perry 0. Smith, Moorestown, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application December 30, 1944, Serial No. 570,662

'1 Claims. (01. 250-495) The present invention relates to electron Some of the objects of a the present invention are to provide an improved image projection; 'to provide means wherein provision is made for dissipating heat which ordinarily impairs the projection of the specimen image; to provide means to prevent drifting of the specimen image while under observation or during photographin of the same; to provide a novel anode structure wherein heat usually detrimental to object viewing or picture taking is no longer effective; and to provide other improvements as will hereinafter appear.

In the accompanying drawings, Fig. 1 represents a fragmentary section on the longitudinal axis of a microscope column showing the interior of the electron gun in association with the object or specimen chamber, said parts embodying one form of the present invention; Fig. 2 represents a sectional enlarged detail on line 2-2 of Fig. l; and Fig. .3 represents a perspective of the heat reflecting plate.

Referring to the drawings, one form of the present invention is shown as assembled upon the column of an electron microscope, the parts necessary for an understanding of the invention being the electron gun l0, and the object chamber unit H. The electron gun I is carried by a housing l2 attached to an annular base 13 adjustably mounted upon the unit I l, and encircling the axially disposed cathode M which is mounted in the apertured tube l5 and electrically insulated from the main or central support of the gun. External connections are provided by leads [6 which extend through glass seals H at the rear end of the gun assembly,

In order to dissipate the heat developed by the electronic bombardment and infra-red radiation, the anode I8 is made of a metal having high heat conductivity, preferably copper, and is of relatively heavy thick wall construction. As shown, the anode I8 is cup shaped and provided with the usual focussing aperture 20, which latter in assembled condition is coaxial with the axis of the microscope column. The annular side wall of the anode l8 has a snug fit within the complemental holeprovided in the casting of the object chamber unit I I, while its outer rim is crimped as shown at 2| into a recess provided in the face of the unit H. In the present instance the anode wall is abnormally long to form a skirt extension presenting a large contact area against the-unit II to carry off rapidly heat from the anode, and is spaced from and coaxially encircles the cathode elements of the gun. Radially disposed ports 22 form communication with the chamber of the unit I I to permit vacuum pumping to take place.

To enhance the heat absorbing properties of the anode, its surface is finished preferably with some black material, such as carbon, graphite, aquadag or a black oxidization product as indicated at 23.

.As a further means of preventing heat from reaching the specimen stage 24, a heat reflecting plate 25 having a highly polished face 26 is suitably mounted between the stage 24 and the anode l8, being spaced from the latter and of a size to bring all parts of the face 26 into juxtaposed relation to the stage end of the anode l8. Thus, a great portion of the heat radiated from the anode towards the stage is thus reflected back to the anode for dissipation as noted above.

From the foregoing it will now be apparent that a novel heat absorbing means has been devised whereby the temperature of the specimen stage, specimen holder, and adjacent parts is kept sufiiciently low as to prevent metals having different coefficients of expansion and contraction from being affected. In the absence of the assembly of the present invention the high temperature of the radiated heat causes these etals to expand and contract unequally so that the stage is constantly in slow motion, and so seriously interferes with the production of sharp photographic images.

I claim as my invention:

1. In an electron microscope, a unit forming an object chamber, a stage in said chamber, an electron gun including cathode and anode electrodes arranged to project an electron beam into said object chamber, and means associated with said anode to so dissipate the heat developed by electronic bombardment and infra-red radiation as to reduce the temperature of heat transmitted to said stage, below the point where unequal expansion and contraction of metal parts within said object chamber takes place.

2. In an electron microscope, a unit forming said object chamber, said anode being madeof copper and mounted in surface contact with said object chamber unit, and a Ireflector plate between said stage and anode to reflect heataway from said stage,

4. In an electron microscope, a unit forming an object chamber, a stage in said chamber, an electron gun including cathode and anode electrodes arranged to project an electron beam into said object chamber, said anode being made of .copper and ;m 0unted insuriace contact with said i hi ct chambemm a d a b a k oa ing on'the surface of said anode. V

$5,.In an el ect ro n microscope, a :unit forming an Object chamber, a stagein said chamber, an

:QlECtI'OIl gunincluding cathodeand anode electrodes arranged to project an electron beam into said "object chamber, and :m ans inc ding 7 a ,rezflector plate betweensaidstage an anode to so dissipate theheat developed by -;electroni c :bombardment and mira-red-radiation as .to reduce the. temperature of ;heat transmitted to said stage, below the point. where @unequalexpansion and contraction of metal parts within said object chamber takes place.

6. In an electron microscope, a unit forming an object chamber, a stage in said chamber, an electron gun including cathode and anode electrodes arranged to project an electron beam into said object chamber, and means including a black coating on said anode to so dissipate the heat developed by electronic bombardment and infra-red radiation as to reducethetemperature of heat transmitted to said stage below the point where unequal expansion and contraction of metal parts within said object chamber takes place.-

7. In an electron microscope, an electron gun including aicathode electrode and an anode electrode, said anoderhaving through ports and an REFERENCES CITED The following references are of record inthe file of :this patent:

UNITED STATES .PA ENT Number m Eat? V,.2:,,234-,28.1 Eli ha, Mar. 11,1941 .c- ,1 ;l8 59.4 Douden M May'2 ,1938 2, 99.;047

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